How Latitude Location on a Micro-World Enables Real-Time Nanoparticle Sizing
We have devised a method for using the nanoparticle induced frequency shift of whispering gallery modes (WGMs) in a microspheroid for the accurate determination of the nanoparticle size in real time. Before the introduction of this technique, size determination from the mode shift could only be obtained statistically based on the assumption that the largest perturbation occurs for binding at the equator. Determining the latitude of the binding event using two polar WGMs results in an analytic method for size determination using a single binding event. The analysis proceeds by incorporating the binding latitude into the Reactive Sensing Principle (RSP), itself containing a shape dependent form factor found using the Born approximation. By comparing this theory with experiments we find that our theoretical approach is more accurate than point dipole theory even though the optical size (circumference/wavelength) is considerably less than one.
KeywordsPolar Mode Wavelength Shift Transverse Electric Whispering Gallery Mode Evanescent Field
The research described herein was supported by the National Science Foundation grant EECS 1303499.
- 1.Arnold, S., Holler, S., & Fan, X. (2015). Taking microcavity label-free single molecule detection deep into the protein realm: Cancer marker detection at the ultimate sensitivity. In Nano-structures for optics and photonics (pp. 309–322). Dordrecht: Springer.Google Scholar
- 11.Khoshsima, M. (2004). Perturbation of whispering gallery modes in microspheres by protein adsorption: Theory and experiment. Doctoral dissertation, Polytechnic University.Google Scholar
- 12.Vollmer, F. (2004). Resonant detection of nano to microscopic objects using whispering gallery modes. Doctoral dissertation, The Rockefeller University.Google Scholar
- 14.Keng, T. K. D. (2009). Whispering gallery mode bioparticle sensing and transport. Doctoral dissertation, Polytechnic Institute of New York University.Google Scholar
- 19.Sobel, D. (2007). Longitude: The true story of a lone genius who solved the greatest scientific problem of his time. New York: Bloomsbury Publishing.Google Scholar